1. Field of the Invention
The present invention relates to the calibration of analysis apparatus and, more particularly, to apparatus for automatically calibrating analyzers of the type which measure a particular characteristic of chemical or biological samples.
2. Description of the Prior Art
A number of systems are presently available for automatically analyzing chemical and biological substances to determine, for example, the presence of glucose in serum, plasma, urine, etc., or the presence of urea-nitrogen in serum. In general, such analyzers utilize various sample changing apparatus in order to advance a plurality of samples through the analyzer. Successful operation of the analyzers, of course, requires proper calibration thereof and this is typically performed by measuring calibration standards having known values of the particular characteristic being measured and adjusting the analyzer output until the known value of the calibration standard is displayed.
Unfortunately, the typical calibration procedures presently employed have not proved satisfactory in all respects. For example, many analyzers must be calibrated by hand. Typically, this requires that an operator manually set the instrument in calibrate mode, manually position the calibration standard for measurement, observe the measurement made of the calibration standard, adjust a calibrate knob on the analyzer control panel until the known value of the calibration standard is displayed, and repeatably measure the calibration standard and readjust the calibrate knob until the actual measurements of the calibration standard conform to the known value thereof. Obviously, manual calibration is time consuming and requires the time and attention of a skilled operator.
In one available analyzer, calibration standards are automatically run through the analyzer to calibrate the same. Typically, it takes three to four minutes to run the standards, and once the run has started it cannot be stopped. Thus, if the instrument fails to calibrate properly, it is necessary to wait for the conclusion of the run, and then repeat the entire operation again. This obviously requires excessive operator time and attention and is wasteful of sample and reagents.
In other analyzers, the calibration standard is measured, and if the calibration is unsatisfactory, an indicator or alarm is enabled to attract the attention of an operator who must then spend time troubleshooting or even manually calibrating the analyzer.